1. Technical Field
The present invention relates to a printed circuit board and an electronic product.
2. Description of the Related Art
As the operating frequencies of electronic products become higher, electromagnetic interference (EMI) has been perceived as a chronic noise problem. Particularly, the operating frequencies of electronic products have reached a few ten MHz, or even a few GHz, making the EMI problems more serious. Subsequently, finding a solution to the problems is desperately needed. Among the EMI problems occurring at a board, a solution for the noise problems particularly occurred at the edge of the board has not been sufficiently researched, making it difficult to completely block the noise at the board.
EMI noise refers to a noise that creates a noise problem caused by interference when an electromagnetic (EM) wave generated in one electronic circuit, component or part is transferred to another electronic circuit, component or part. The EMI noise can be broadly categorized into two types, namely radiation noise (reference numerals 110 and 130 in FIG. 1) and conduction noise (reference numeral 120 in FIG. 1).
The EMI noise radiated from a board of an electronic product may be commonly shielded by covering an upper portion of the board by use of a shield can (40 of FIG. 2) or by absorbing the EMI noise by attaching an EMI field absorber (42 of FIG. 3). However, in the case of using the shield can 40, since a new radiation noise 10′ is generated due to the antenna effect, it is difficult to shield all EMI noises radiated towards the outside of the board, and there are limitations to frequency ranges that can be absorbed by the EMI field absorber 42, making it urgently needed to find an effective shielding method.
The shield can 40 has some problems in attaching itself. Furthermore, not only is the thickness of the shield can restricted, but also the shield can increases the weight of a lightweight electronic device. Also, in the case of the EMI field absorber 42, it is difficult to develop a material that can shield the EMI noise in various frequencies, and it may take longer to develop the material, thereby increasing the production cost.
Therefore, it is desperately needed to find a solution that can readily absorb various frequencies, be easy to apply without any antenna effect and be cost-effective in manufacturing.